A photo-detecting device is a device such that includes a plurality of photodiodes that are one-dimensionally or two-dimensionally arranged on the light-receiving surface, and an integrating circuit having an amplifier and a capacitor; there are some cases that include further a signal processing circuit at the later stage of the integrating circuit. In this photo-detecting device, electric charge corresponding to the intensity of incident light is outputted from the photodiode, and that charge is stored in the capacitor. Then, a voltage corresponding to a quantity of the stored electric charge is outputted from the integrating circuit. Thus, when the voltage is measured corresponding to the electric charge generated at each of the plurality of photodiodes, light to be incident upon the light-receiving surface arranged by the plurality of photodiodes can be detected.
For example, a photo-detecting device described in JP-A2001-24253 (Document 1) is known as the aforementioned one. In the photo-detecting device disclosed in Document 1, one integrating circuit is provided for a plurality of photodiodes, and a switch is provided between each photodiode and the input terminal of the integrating circuit. In addition, in this photo-detecting device, the plurality of photodiodes are formed on a first substrate, the integrating circuit is formed on a second substrate, and the rim portions of the first and second substrates are connected to each other by a bonding wire. Then, when each of the plural switches is closed sequentially, an electric charge generated in each of the plurality of photodiodes on the first substrate is inputted sequentially in the integrating circuit on the second substrate, and a voltage corresponding to the electric charge is outputted sequentially from the output terminal of the integrating circuit. This photo-detecting device enables an increase of the number of pixels and advanced high density.